Numerical Simulation And Enhancement Of Internal Pressure Type Vacuum Membrane Distillation By CFD

Membrane distillation(MD)is a membrane separation technology combined with the theory of evaporation.Because of the low operation energy consumption and the reuse of water resources,MD has drawn much attention in recent years.In the course of researching the treatment of desulfurization wastewater,the research group found that vacuum membrane distillation(VMD)has larger membrane flux,which is simple and easy to operate with good development potential.However,due to the limitation of gas production efficiency,the promotion in engineering application is not good.Therefore,based on the previous research of the research group,this paper explores the tube-side vacuum membrane distillation by CFD technology,which provides a new way and theoretical basis for the subsequent product development.The main contents of this paper include:(1)Based on the experimental components,a basic model which can be used in the numerical simulation of MD process was established and the operation was carried out by ANSYS-FLUENT.The simulation results are in good consistent with the experimental data,and the relative error is within the acceptable range of engineering application.The research results have practical guiding significance for the process operation,indicating that it is feasible to Research the tube-side vacuum membrane internal pressure type vacuum membrane distillation through CFD technology.(2)The membrane distillation process is divided into two stages,the factors that affect the phase transition were investigated.The results show that increasing the flow,temperature and vacuum degree can promote the membrane distillation process,but the effect of temperature and vacuum degree is obviously greater than the flow rate.Under conditions such as feasible operation and economical permission,therefore,increasing the flux of the membrane should be mainly based on temperature and vacuum factors.(3)The outer surface of membrane was set as the gas inlet,the flow field and the impact of distribution of the membrane and gas outlet were studied.The results show that the distribution of vapor in the membrane module is approximately symmetrical.Secondly,for the current gas production efficiency of MD,the distribution of membrane and gas outlet have little effect on the gas extraction process.Therefore,to promote phase transition is the main direction of enhanced membrane distillation process(4)Through the research on the two-phase flow VMD(TVMD)process,it was found that the two-phase flow(uniform mixing micron bubbles)has good performance in improving the membrane flux and TVMD is more suitable for the low energy consumption condition,is a better way to strengthen the MD process.Similar to the single-phase flow VMD,the increase of temperature and vacuum degree on the membrane flux is stronger than the flow factor.In addition,there is an optimum bubble diameter and gas volume that maximizes the enhancement of the MD process.This paper confirmed the feasibility of using CFD technology to research the tube-side VMD.Compared with the experiment,the numerical simulation can save a lot of resources and shorten the product development cycle.In addition,this paper verified the enhanced effect of two-phase flow on the MD process,provided theoretical basis for the subsequent research,and advanced the promotion of membrane distillation technology in engineering applications and productization.